1. Field of the Invention
The present invention relates generally to a modular jack for high-speed communications, capable of transmitting up to 250 MHz per pair in UTP 4 pair cable and, more particularly, to a crosstalk canceling pattern for high-speed communications and a modular jack having the same, which includes an additional compensating capacitor on a transmission line adjacent to IDC terminals so as to correct phase mismatch due to inductance generated in insert pins and transmission lines, in addition to canceling first parasitic capacitance generated between neighboring insert pins, when a high-frequency signal is applied to the modular jack for high-speed communications, thus satisfying performance requirements for Category 6, and eliminating a soldering process, therefore ensuring a high quality when used in a network.
2. Description of the Related Art
Generally, when a user desires to transmit data or voice using a terminal, such as a computer or a telephone, the terminal must be connected to a communication cable, which extends into an apartment unit or an office. A modular plug and a modular jack have been used as a connection means.
FIG. 1 is an exploded perspective view showing an example of a conventional modular jack. As shown in the drawing, the conventional modular jack 1 includes a housing 10 and a connector 20 mounted to the rear surface of the housing 10.
The housing 10 is produced by forming a synthetic resin material. A plug insert hole 11 is formed in the front surface of the housing 10 so that a modular plug 2 is inserted into the plug insert hole 11. A mounting part is provided on the rear surface of the housing 10 so that the connector 20 is mounted to the housing 10. The connector 20 serves to electrically connect the modular plug 2 to an incoming cable. An insert 60 is provided to one side of the connector 20 to be electrically connected to a terminal of the modular plug 2, and a plurality of IDC terminals 51 is provided to an opposite side of the connector 20 to be connected to the incoming UTP cable. Further, the insert 60 and the IDC terminals 51 are electrically connected to each other through transmission lines formed on a printed circuit board 50. Meanwhile, an IDC-type terminal block 30 is coupled to the IDC terminals 51 to allow the IDC terminals 51 to be easily connected to a wire of the UTP cable. A contact block 40 is mounted on the IDC-type terminal block 30 to press and insert the wire.
Thus, the wire W of the UTP cable is connected to the IDC terminals 51 through the IDC-type terminal block 30 and the contact block 40. When the modular plug 2 is inserted into the plug insert hole 11 of the housing 10, the terminal of the modular plug 2 is connected to insert pins 61 of the insert 60, thus permitting data or voice communication.
FIG. 2 is a sectional view showing the connector 20 of the conventional modular jack.
As shown in the drawing, the insert 60 is installed on one side of the printed circuit board 50 having a predetermined size, and the IDC terminals 51 are vertically installed on an opposite side of the printed circuit board 50. In this case, the insert 60 includes an insert body 62 and a plurality of insert pins 61 secured to the insert body 62. The insert pins 61 are electrically connected to the transmission lines through contact holes which are formed in the printed circuit board 50. Further, in order to cancel crosstalk due to parasitic capacitance generated between neighboring insert pins 61, a compensating capacitor 52 is provided on the printed circuit board 50. The compensating capacitor 52 comprises leads which are arranged near each other and have a predetermined length so as to generate an inverse-phase capacitance on a corresponding transmission line.
Thus, as shown in the equivalent circuit diagram of FIG. 2, when a low-frequency signal is applied to the conventional modular jack 1, parasitic capacitance A is generated between neighboring insert pins 61, which are pressed by the terminal of the modular plug 2 to be parallel to each other, so that crosstalk is generated. However, the crosstalk generated in the insert pins 61 is canceled by inverse-phase capacitance C which is generated in the compensating capacitor 52 formed on the printed circuit board 50. Thus, the conventional modular jack 1 can perform low-speed communication under 100 MHz, for example, satisfying the performance requirements for Category 5.
However, as shown in the equivalent circuit diagram of FIG. 3, when the high-frequency signal exceeding, for example, 250 MHz, is applied to the conventional modular jack 1, first and second parasitic inductance B and D is generated in the insert pins 61, the transmission line between the insert pins 61 and the compensating capacitor 52, and the transmission line between the compensating capacitor 52 and the IDC terminals 51. That is, the first parasitic inductance B is generated in the insert pins 61 and the transmission line between the insert pins 61 and the compensating capacitor 52, while the second parasitic inductance D is additionally generated in the transmission line between the compensating capacitor 52 and the IDC terminals 51.
As such, since-impedance hindering the current flow in the insert pins and the transmission lines, that is, reactance, is increased in a high-frequency area, it is impossible to completely cancel crosstalk simply by forming the compensating capacitor 52 on the printed circuit board 50. Thus, the conventional crosstalk canceling pattern and modular jack are problematic in that it is impossible to satisfy the performance requirements for Category 6, whose maximum transmission frequency is 250 MHz or higher.
Further, the insert pins 61 and the IDC terminals 51 passing through the printed circuit board 50 are secured to the lower surface of the printed circuit board through soldering, and are connected to the transmission lines. At this time, a canceling pattern formed on the printed circuit board may be stained with flux, used to prevent surface oxidation due to high temperature during a soldering process, so that contact points are unstable, thus leading to poor contact. Further, it reduces insulation resistance value. In order to avoid such a problem, a post operation is required.